A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
A CD-ROM Appendix containing a computer program listing is submitted on a compact disc, which is herein incorporated by reference in its entirety. The total number of compact discs including duplicates is two. Appendix A, which is part of the present specification, contains a list of the files contained on the CD-ROM Appendix.
1. Field of the Invention
The present invention relates to a system that connects an optical head to additional electronics in an optical drive.
2. Description of Related Art
A conventional optical drive (e.g., a compact disk player) typically includes a stationary optical unit, a movable optical unit, and an actuator. The stationary optical unit generally includes a laser diode, a half mirror, and a photodetector. The laser diode generates a light beam that is reflected by the half mirror onto the movable optical unit. The movable optical unit typically includes an objective lens that focuses the light beam on a spinning optical disk.
The actuator aligns the movable optical unit with the tracks of the optical disk so that the light beam reflects off the lands and pits of the tracks. The reflected light beam travels back through the movable optical unit and back to the stationary optical unit. The light beam is transmitted through the half mirror onto the photodetector where the varying intensity of the light is changed to electrical signals.
Optical drives are becoming smaller so they can be integrated into portable devices including laptop computers and personal digital assistants (PDAs). Close arrangement and integration of components help to miniaturize optical drives. For example, the stationary and movable optical units described above can be integrated into a single component (an integrated optical head) called xe2x80x9coptical pickup unitxe2x80x9d or xe2x80x9cOPUxe2x80x9d. The OPU can be mounted on a small actuator arm that places the OPU over the tracks of the spinning medium with relatively small forces.
The miniaturization of the optical drive creates new design restraints on the flex circuit that carries signals to and from the OPU. Depending its shape and the location from which it departs from the actuator arm, the flex circuit may constrain or disturb the movement of the actuator arm carrying the OPU. Accordingly, what is needed is a system that connects the OPU to the remaining electronics of the optical drive without impinging on the motion of the actuator arm.
In one embodiment of the invention, an optical assembly includes a base plate and an actuator arm. The actuator arm includes a tracking section pivotally mounted around a tracking axis to the base plate, and a focus section pivotally mounted around a focus axis to the tracking section. A proximate end of a service loop extends from the focus section while a distal end of the service loop is mounted to the base plate. When the tracking section rotates around the tracking axis, at least a portion of the service loop bends. When the focus section rotates around the focus axis, at least a portion of the service loop twists.
In another embodiment of the invention, a method predicts the shape of a service loop that does not rotate the actuator arm from a resting position. The method uses a number of beam elements deflected by the actuator arm to simulate the shape of the service loop. In order for the service loop not to rotate the actuator arm, the method assumes that the actuator arm applies an equivalent force through the rotation axis. A user provides a mounting point (the point where a first end of the service loop is mounted to a base plate), a mounting angle (the angle at which the first end of the service loop is mounted to the base plate), a departure point (the point where a second end of the service loop is mounted to the actuator arm), a departure angle (the angle at which the second end of the service loop is mounted to the actuator arm), the total number of the beam elements, and the beam stiffness. The user also provides initial values for the beam length and the magnitudes of the X and Y components of the force applied by the actuator arm. For each beam element, the method calculates a start position, a start angle (the angle at which the start of the beam is oriented), an end position, and a finish angle (the angle at which the end of the beam is oriented under deflection). If the end position and the finish angle of the last beam element do not match the desired end position and angle of the service loop, the method repeats the above steps with new values for at lest one of the beam length and the magnitudes of the X and Y components.
In yet another embodiment, a method calculates the restoring torque when the actuator arm is rotated away from its resting position. Unlike the above method, this method assumes that a moment exists around the rotation axis. In one implementation, the moment around the rotation axis is expressed as the product of the Y component and its X direction offset from the rotation axis. Thus, the user provides initial values for the offset of the Y component and the magnitudes of the X and Y components. The user also provides the mounting point, the mounting angle, the departure point, the departure angle, the total number of the beam elements, the beam stiffness, and the beam length. For each beam element, the method calculates a start position, a start angle, an end position, and a finish angle. If the position of the last beam element does not match the desired end position and angle of the service loop, the method repeats the above steps with new values for at least one of the offset of the Y component and the magnitudes of the X and Y components.